Added support for improvement_direction to relevant values, which is propogated to chartjson.

tools/perf/benchmarks/dom_perf.py

Index: tools/perf/benchmarks/dom_perf.py
diff --git a/tools/perf/benchmarks/dom_perf.py b/tools/perf/benchmarks/dom_perf.py
index 87c0bcb7e58dbde2256cd270aa6d7d4ee828bab6..3bec542d529fd5b8baad2541de516cbed3ce39dd 100644
--- a/tools/perf/benchmarks/dom_perf.py
+++ b/tools/perf/benchmarks/dom_perf.py
@@ -11,6 +11,7 @@ from telemetry import page as page_module
 from telemetry.core import util
 from telemetry.page import page_set
 from telemetry.page import page_test
+from telemetry.value import improvement_direction
 from telemetry.value import merge_values
 from telemetry.value import scalar
 
@@ -55,7 +56,8 @@ class _DomPerfMeasurement(page_test.PageTest):
         if len(suite['Benchmarks']) or suite['score']:
           results.AddValue(scalar.ScalarValue(
               results.current_page, '%s.%s' % (suite['name'], SCORE_TRACE_NAME),
-              SCORE_UNIT, suite['score'], important=False))
+              SCORE_UNIT, suite['score'], important=False,
+              improvement_direction=improvement_direction.UP))
     finally:
       tab.EvaluateJavaScript('document.cookie = "__domperf_finished=0"')
 
@@ -68,7 +70,8 @@ class _DomPerfMeasurement(page_test.PageTest):
     total = _GeometricMean(combined_score.values)
     results.AddSummaryValue(
         scalar.ScalarValue(None, 'Total.' + SCORE_TRACE_NAME, SCORE_UNIT,
-                           total))
+                           total,
+                           improvement_direction=improvement_direction.UP))
 
 
 @benchmark.Disabled('android', 'linux')